1. Field of the Invention
The invention relates to an induction system for supplying an internal combustion engine with combustion air, in particular for a motor vehicle, having at least one separate air manifold, from which in each case cylinder-specific induction pipes lead to air intakes of cylinders of the internal combustion engine.
2. Discussion of the Prior Art
It is known from Asia-Pacific Automotive Report, volume 234, May 4, 1996, to use two switchable valves to switch a tuned pipe long or short and thus to change a corresponding tuned length as desired. However, this system only switches between two different tuned states, ensuring optimum cylinder filling only over a limited speed range. For this reason, a third switchable valve is provided, which in the open state increases a cross section of flow for combustion air accordingly, so that at high revs a high mass flow is ensured. However, this completely destroys any tuned effect in the induction system for the combustion air and does not provide any kind of assistance for-filling the cylinders.
The present invention is therefore based on the object of providing an induction system of the above type in which the above drawbacks are overcome and of achieving optimum cylinder filling with combustion air over the maximum possible speed range of the internal combustion engine.
To this end, according to the invention the induction pipes are designed as ram pipes for upper speed ranges of the internal combustion engine and at least one balancing valve is arranged in the air manifold, which valve optionally, in the closed position, divides the air manifold to form a long preintake length or, in the open position, instead of a long preintake length provides an air manifold with an increased volume.
This has the advantage that, in a structurally simple, space-optimized manner, it is optionally possible to achieve a tuned-intake charging for low speed ranges of the internal combustion engine, by closing the balancing valves, or to achieve a ram-type charging for high speed ranges of the internal combustion engine, by opening the balancing valves.
For internal combustion engines with cylinders which are arranged on separate cylinder banks, for example in the case of an 8-cylinder engine in a V or double-V arrangement or VR arrangement, it is particularly advantageous to provide two separate air manifolds.
An additional tuned state for a middle speed range of the internal combustion engine is achieved by the fact that in each case two air manifolds are connected to one another via a tuned pipe, the tuned pipe having a tuned valve for optionally opening or closing the pipe in such a manner that the respective air manifolds are optionally connected or not connected to one another via the tuned pipe.
In a preferred embodiment, the internal combustion engine has a crankshaft with a 180xc2x0 crank angle and n cylinders, in which, to ensure that there is no disruption to the induction processes, the cylinders 1 to n/2 are connected to a first air manifold via respective induction pipes and the cylinders (n/2+1) to n are connected to a second air manifold via respective induction pipes.
Preferably, n=4 or 8. In the latter case, an ignition sequence for the cylinders 1 to 8 is, for example, as follows: 1-5-2-6-4-8-3-7.
A particularly small space requirement as the result of a compact design is achieved by the fact that the cylinders are distributed, for example, over at least two cylinder banks, in particular over two double cylinder banks, each air manifold supplying cylinders of one cylinder bank or one double cylinder bank with combustion air, and the induction pipes of the first air manifold crossing those of the second air manifold.
In this case, the balancing valve and the induction pipes of an air manifold are expediently arranged in such a manner that, when the balancing valve is closed, there is an increasing induction length for the cylinders which are supplied in each case via the induction pipes as the cylinder number increases.
In another preferred embodiment, the internal combustion engine has a crankshaft with a 90xc2x0 crank angle and n cylinders, in each case n/2 or (nxe2x88x921)/2 of the cylinders being connected to a first air manifold via respective induction pipes and the other n/2 or (n+1)/2 cylinders being connected to a second air manifold via respective induction pipes.
Expediently, n=4 or 8. In the latter case, an ignition sequence of the cylinders 1 to 8 is, for example, as follows: 1-5-7-4-8-3-2-6.
In this case, to ensure that there is no disruption to the induction processes, the cylinders 1, 2, 7, 8 are preferably connected to the first air manifold and the cylinders 5, 6, 3, 4 are preferably connected to the second air manifold.
A particularly small space requirement as a result of a compact design is achieved by the fact that the cylinders are distributed over at least two cylinder banks, in particular over two double cylinder banks, the air manifolds being arranged in each case adjacent to one cylinder bank or double cylinder bank and opposite to the other cylinder bank or double cylinder bank, in which arrangement some of the induction pipes of one air manifold lead to the opposite cylinder bank or double cylinder bank, crossing over the induction pipes of the other air manifold, and some of these induction pipes lead to the adjacent cylinder bank or double cylinder bank in an overhead arrangement.